A bead portion of a tire is repeatedly deformed largely during running. Therefore, temperature of the bead portion during running is raised. Such temperature rise deteriorates rubber of the bead portion and the rubber is destroyed in some cases. Therefore, to enhance the durability of the tire, it is necessary to prevent the temperature rise of the bead portion.
To suppress the temperature rise of the bead portion, attempts have been made to enhance the rigidity of the bead portion and to reduce the deformation itself during running. However, this method has problems that a tire mass is increased, a kinematic performance is lowered, and fuel economy is deteriorated.
The present inventors have earnestly repeated researches and as a result, they have found that if convex portions extending in a direction intersecting with a circumferential direction are provided at intervals in the circumferential direction on an outer surface in the rotation axis direction which does not come into contact with the tire, of a flange of the wheel rim and/or on a radially inner surface of a rim body, the heat-dissipating performance of the rim body is markedly enhanced and, as a result, it is possible to suppress temperature rise of the bead portion of the tire which comes into contact with the rim body or of air in a tire cavity, and to enhance the durability of the tire. Thus, the inventors have accomplished the present invention. Examples of prior arts concerning the wheel rim are as follows:    Patent Literature 1: JP-A-6-135202    Patent Literature 1: JP-A-8-216604    Patent Literature 1: JP-A-5-338402